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15 June 2024, Volume 41 Issue 6 Previous Issue    Next Issue

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Contents 2024, 41 (6):  0-0.  Abstract ( 60 )   PDF (25616KB) ( 54 )   Related Articles | Metrics

Land and Water Resources

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Spatio-temporal characteristics and trends of area changes in the small and medium-sized lakes in Xinjiang, China, from 1991 to 2020 MA Yuanzhi, QIN Xiaolin, LING Hongbo, YAN Junjie, ZHANG Guangpeng 2024, 41 (6):  905-916.  doi: 10.13866/j.azr.2024.06.01 Abstract ( 212 )   HTML ( 25 )   PDF (11714KB) ( 104 )   Lakes, as integral components of the terrestrial ecosystems, are vital for regional economic growth and ecological security. Previous studies have primarily focused on typical or large lakes in the Xinjiang region, with comparatively less attention given to smaller lakes. This study analyzed the area dynamics of 74 small and medium-sized lakes in Xinjiang from 1991 to 2020, conducting a comprehensive analysis of the lakes at varying altitudes and with diverse geographical characteristics. The research uncovered that during 1991-2020, the total area of lakes in Xinjiang expanded from 167.98 to 400.51 km², with the most significant growth observed in the mountainous lakes. Monthly scale analysis revealed pronounced seasonal characteristics in the area-changes of these mountainous lakes. Statistical analysis indicated divergent responses of lakes at varying altitudes to climatic changes. The substantial enlargement of lakes in Xinjiang’s mountainous regions is primarily attributed to climate change, particularly the rise in average annual temperatures. In the plains, human activities, especially irrigation, were identified as the primary drivers of lake-area changes, while the impact of climatic factors was relatively minor. Figures and Tables | References | Related Articles | Metrics

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Analysis of the hydrochemistry characteristics and groundwater recharge sources in the Hotan River Basin, China LI Xiaodeng, CHANG Liang, DUAN Rui, WANG Qian, ZHANG Qunhui, YANG Bingchao 2024, 41 (6):  917-927.  doi: 10.13866/j.azr.2024.06.02 Abstract ( 147 )   HTML ( 7 )   PDF (9810KB) ( 214 )   The characteristics of hydrochemistry and groundwater recharge in the Hotan River Basin were studied by analyzing the chemical composition of water, primary recharge sources, and mutual transformation of water bodies (wells, ponds, and rivers) in the different geomorphic units. For this, SPSS statistical analysis, Piper diagram, Gibbs diagram, and isotope tracing methods (D, 18O, and 14C) were used. The results showed that (1) the water bodies mainly originated from the ice- and snow-meltwater and precipitation in the mid and high mountainous areas>2000 m in the south. From the mountains to the desert, the chemical type and salinity of the groundwater showed obvious zonal characteristics. The different water bodies were weakly alkaline, and the ion composition and TDS values varied with the overall order of pond>well>river. The NO3- contents of a few groundwater samples were significantly abnormal. (2) the groundwater in the gravel plain area mainly received vertical and disconnected recharge from the surface river water. The groundwater had a fast renewal rate, low salinity, and major water-rock interactions, mainly of the SO4·Cl-Ca·Mg type. (3) the TDS value of the groundwater in the fine soil plain area varied over an extensive range, mostly of the Cl·SO4-Na type. In the inter-river block, the groundwater near the upstream received surface water and lateral runoff from the adjacent areas, and the 14C age was small. “Drift Oxygen” of δD and δ18O isotopes in the groundwater of the middle and lower reaches could be generally observed. The 14C age of the groundwater in the watershed was considerable but minuscule near the riverbank. The relation between the groundwater and the river was close. On both sides of the inter-river block, the groundwater runoff flowed along the northeast and northwest directions, respectively, and finally discharged into the peripheral desert area. The research results can provide a theoretical basis for the reasonable development and utilization of water resources and protect the ecology and environment of the Hotan River Basin. Figures and Tables | References | Related Articles | Metrics

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Analysis of runoff changes and attribution in the main stream of Zuli River in the past 65 years LIANG Shuanghe, NIU Zuirong, JIA Ling 2024, 41 (6):  928-939.  doi: 10.13866/j.azr.2024.06.03 Abstract ( 121 )   HTML ( 13 )   PDF (13369KB) ( 50 )   Based on the measured annual and monthly runoff data of Huining, Guochengyi and Jingyuan stations in the main stream of Zuli River from 1957 to 2021, the variation characteristics and driving factors of runoff at different time scales in Zuli River Basin were analyzed by linear tendency estimation, Mann-Kendall test and wavelet analysis. The results showed that: which are mainly influenced by human activities and climatic factors. (1) The runoff of the main stream of the Zuli River showed a decreasing trend from 1957 to 2021, and the runoff has decreased by 52.9% over the past 30 years. (2) The measured annual runoff of the three hydrological stations of Huining, Guochengyi, and Jingyuan underwent abrupt changes in 1992, 1984, and 1994, respectively. (3) Runoff and precipitation showed similar cycles of abundant and low state at the three stations of the main stream of Zuli River. The analysis results show that the reduction of measured annual runoff in the main stream of the Zuli River is mainly affected by human activities such as soil and water conservation measures, followed by climatic factors such as the reduction of precipitation, of which human activities and climate change contribute to the reduction of runoff by 74.47% and 25.53%, respectively. Figures and Tables | References | Related Articles | Metrics

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Monitoring the glacier changes in Yilian Habirga Mountain using Sentinel-2 data LI Ruonan, LI Junli, LI Shuangshuang, LIU Shuaiqi, DU Weibin 2024, 41 (6):  940-950.  doi: 10.13866/j.azr.2024.06.04 Abstract ( 126 )   HTML ( 12 )   PDF (17820KB) ( 86 )   High-resolution time-series remote sensing plays a vital role in monitoring glacier changes. In this paper, Sentinel-2 multitemporal satellite images from 2016-2022 were used along with the D-UNet semantic segmentation model to extract the glacier change information of Yilian Habirga. These results were compared with the Landsat remote sensing data of the similar temporal phase to ascertain any differences in the accuracies of Sentinel-2 and Landsat for glacier mapping. Based on these findings, 75 typical glaciers were selected to analyze the change-related characteristics of the total glacier area and glacier end in the recent study area. The results show that (1) The overall accuracy of Sentinel-2 glacier mapping was 95.0%, which is 5%-10% higher than Landsat-8 under the same conditions. (2) The average area retreat rate of glaciers in the study area from 2016 to 2022 was 0.75%±0.69%·a-1, in which the region<4600 m above sea level was that of glacier area reduction; the lower the altitude, the greater the area retreat rate. (3) In the last 6 years, the average heights of the 75 typical glacier ends rose by 17.75 m, and the average lengths reduced by 11.39 ± 2.36 m·a-1. Among these, the retreats in the west, northeast, and south were the most significant, which were 15.49 ± 2.36 m·a-1, 13.95 ± 2.36 m·a-1, and 13.14 ± 2.36 m·a-1, respectively; the rate of the glacier end retreated with an increase in the elevation and the decreased. Figures and Tables | References | Related Articles | Metrics

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Land use intensity change and its influence on evapotranspiration in Aksu River Basin from 2000 to 2020 YAO Xiaochen, GAO Fan, HAN Fanghong, HE Bing 2024, 41 (6):  951-963.  doi: 10.13866/j.azr.2024.06.05 Abstract ( 125 )   HTML ( 17 )   PDF (10658KB) ( 46 )   It is of great significance for scientific management and efficient utilization of water resources in the basin to deeply explore the information of internal conversion process of land use types, measure the impact of land use change intensity on evapotranspiration, and accurately evaluate the temporal and spatial variation of ET. Based on the intensity analysis model, the intensity change characteristics of land use types at different levels in the Aksu River Basin from 2000 to 2020 and their impact on the actual evapotranspiration of the basin were revealed. The results showed that : (1) At the time interval level, the intensity of land use change in the basin increased first and then decreased, and the change was the most active from 2000 to 2005. At the land type level, the increase and decrease of cultivated land, construction land, water area and forest land area are more active. The increase of cultivated land area at the transfer level mainly comes from grassland (54.31%) and unused land (26.26%). (2) The average annual evapotranspiration of the basin is 166.56 mm. The interannual fluctuation is large, and the overall trend is increasing, with an annual growth rate of 3.68 mm·a-1. Evapotranspiration from April to October accounted for 71.76% of the annual evapotranspiration. The high value of actual evapotranspiration is distributed in mountainous forest land and cultivated land in plain area, and the low value area is distributed in piedmont desert area and oasis and desert transition zone. (3) The results of principal component analysis show that the driving force of ETa change in Aksu River Basin is the conversion intensity of grassland, cultivated land and unused land. The correlation coefficient between land use change intensity and actual evapotranspiration is 0.87, and there is a strong correlation between the two. Figures and Tables | References | Related Articles | Metrics

Plant Ecology

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Characteristics of the spatial and temporal evolution of Gross Primary Productivity and its influencing factors in China’s drylands TANG Kexin, GUO Jianbin, HE Liang, CHEN Lin, WAN Long 2024, 41 (6):  964-973.  doi: 10.13866/j.azr.2024.06.06 Abstract ( 154 )   HTML ( 5 )   PDF (12439KB) ( 63 )   This study aimed to clarify the carbon sequestration capacity and its change mechanisms in the drylands of China. The study used the AI index to delineate the extent of drylands. Based on the MODIS Vegetation Gross Primary Productivity (GPP) dataset, the temporal and spatial characteristics of vegetation carbon sequestration capacity in China’s drylands from 2001 to 2020 were investigated. This investigation considered meteorological data, including temperature, precipitation, Vapor Pressure Deficit (VPD), soil water content, and human activities such as land use. The results reveal the following: (1) Over the 20 year period, GPP in China’s drylands elevated significantly in 64.72% of the regions. (2) Temperature had the lowest impact on GPP, with a relative contribution rate of 21.70%. Precipitation and soil water content emerged as the dominant factors driving GPP growth, with their combined contribution rate exceeding 55%. As drought intensified, the effect of water stress gradually strengthened. In different vegetation types, except for mixed forests and alpine vegetation, precipitation was the most critical climate factor influencing GPP changes. (3) Differences in soil and landform types were the dominant factors influencing the spatial variation of GPP. Moisture and land use type factors also played important roles, with the explanatory power of the interaction between any two factors exceeding that of a single factor. The interaction between soil type and the other factors was particularly remarkable. The study’s findings hold essential theoretical implications for a deeper understanding of the evolution characteristics of carbon sinks in arid ecosystems in China and their response mechanisms to external environmental factors. Figures and Tables | References | Related Articles | Metrics

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Carbon density distribution pattern and its factors of the artificial forest vegetation in opencast coal mine ZHANG Jianhua, ZHOU Xiaoyang, GUO Xuting, DU Xinxin, AN Li, QIN Hao, LIU Yong, ZHANG Hong, XU Longchao 2024, 41 (6):  974-983.  doi: 10.13866/j.azr.2024.06.07 Abstract ( 111 )   HTML ( 15 )   PDF (2848KB) ( 66 )   This study aimed to quantitatively analyze the distribution patterns of carbon density and its factors of artificial forest vegetation in opencast coal mines and provide a basis for improving the forest carbon (C) sink service function using available data. It selected Pinus tabulaeformis, Populus microphylla, Populus canadensis, Robinia pseudoacacia, Ulmus pumila, and mixed R. pseudoacacia-U. pumila plantations in the waste dump of the Antaibao mining area as the research objects. The biomass carbon density and spatial distribution pattern of each plantation were measured based on the field investigation data and by employing allometric approaches. The carbon density of the P. canadensis plantation was 36.95 t∙hm-2, significantly higher than others (P<0.05). The carbon density was markedly higher in the thickly planted P. tabulaeformis forest than in the sparsely planted one (P<0.05). The overall carbon density of each component in the artificial forest was as follows: tree layer>litter layer>herbaceous and shrub layers (P<0.05). The tree layer accounted for 78.3%-93.6% of the vegetation carbon density, indicating it has the highest carbon density in the artificial forest vegetation. The carbon density in the trunk of the tree layer was remarkably greater than that of the roots, branches, and leaves (P<0.05). The carbon density in the trunk of P. canadensis plantation was conspicuously higher than that of R. pseudoacacia and R. pseudoacacia-U. pumila. Similarly, the carbon density was significantly higher in the trunk of the sparsely planted P. tabulaeformis forest than in the densely planted forest. The carbon density of the tree and litter layers demonstrated a remarkable positive correlation with the stand density of artificial forests and negatively with the height and coverage of herbs. Additionally, the carbon density of the tree layer was markedly positively correlated with the tree height (P<0.05). From the perspective of carbon sequestration function, a reasonable and dense planting of P. tabulaeformis and P. canadensis in the Antaibao coal mine waste dump is beneficial for the ecological restoration of the area, thus achieving sustainable development of the ecology and environmental security. Figures and Tables | References | Related Articles | Metrics

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Response of soil nitrogen mineralization to temperature along the different successional stages in Xinglong Mountain, Gansu Province, China TANG Weichun, LIU Xiao’e, SU Shiping, TIAN Xiaojuan, TANG Qingtong, ZHANG Jing 2024, 41 (6):  984-997.  doi: 10.13866/j.azr.2024.06.08 Abstract ( 116 )   HTML ( 6 )   PDF (17972KB) ( 41 )   Soil nitrogen mineralization is a crucial process of the soil nitrogen cycle, with temperature being one of the most important factors affecting soil nitrogen mineralization. Studying the effect of temperature on soil nitrogen mineralization characteristics in different successional stages is of great significance for understanding the soil nitrogen cycle in terrestrial ecosystems. In this study, the communities in different successional stages of Xinglong Mountain in Gansu Province were selected as the research objects. The indoor, constant temperature, aerobic culture method was used to study the soil nitrogen mineralization characteristics of five successional stages: grasslands, shrub forests, Betula platyphylla forests, Picea wilsonii-Betula platyphylla forests, and Picea wilsonii forests under temperatures of 15 ℃, 25 ℃, and 35 ℃. The results showed that (1) except for the soil at a depth of 0-20 cm in grasslands, the increase in the soil nitrogen mineralization rate of the other successional stages was directly proportional to the temperature, and the cumulative mineralization of soil nitrogen in the different successional stages showed a similar trend. (2) with the positive advancement of succession, the soil nitrogen mineralization rate and cumulative mineralization amount of different successional stages initially enhanced but then diminished. The soil nitrogen mineralization rate of B. platyphylla forests was the highest, which was 1.63-, 1.61-, 1.25-, and 1.47- times more than that of grasslands, shrub forests, P. wilsonii-B. platyphylla forests, and P. wilsonii forests, respectively. The soil nitrogen mineralization rate and cumulative mineralization amount of P. wilsonii-B. platyphylla forest were the highest, which were 0.68-, 0.72-, 0.84-, and 0.97-times greater than those of grasslands, shrub forests, B. platyphylla forests, and P. wilsonii forests, respectively. (3) the soil nitrogen mineralization rate and cumulative mineralization were inversely proportional to the soil depth, with the maximum detected at a depth of 0-20 cm. (4) the temperature sensitivity coefficient (Q10) at 15 ℃ and 25 ℃ in different successional stages varied markedly (P<0.05). The Q10 at first decreased and then increased in relation to the positive succession. The Q10 between the communities in different succession stages at 25 ℃ and 35 ℃ did not alter remarkably (P>0.05). The results of this study provide a theoretical basis for evaluating the evolution of soil quality and the dynamic changes in the soil nitrogen supply capacities in the community. Figures and Tables | References | Related Articles | Metrics

Ecology and Environment

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Carbon sequestration potential of oasis ecosystem in Xinjiang, China ZHANG Haozhe, XUE Yayong, MA Yuanyuan, XUE Guoxuan 2024, 41 (6):  998-1009.  doi: 10.13866/j.azr.2024.06.09 Abstract ( 131 )   HTML ( 18 )   PDF (15369KB) ( 60 )   Net Primary Productivity (NPP) is an essential indicator of the terrestrial carbon (C) cycle, which can reflect the carbon sink capacity of terrestrial ecosystems. In the face of China’s “double carbon” goal of “carbon peak” and “carbon neutrality,” improving the carbon sequestration capacity of the terrestrial ecosystems is one of the crucial ways. Due to its vast geographical area and considerable vegetation restoration potential, it is of great practical significance to evaluate the current situation of carbon sequestration in Xinjiang and explore the potential of carbon sequestration so as to respond positively and realize the national “double carbon” goal. This study combined the Carnegie Ames Stanford Approach (CASA) model with the land use, remote sensing, and meteorological (temperature, precipitation, and solar radiation) data, and NPP in Xinjiang from 2001 to 2020 for the simulation. The Sen-MK method was used to analyze the trend in NPP changes. Pearson correlation analysis was used to identify the relationship between NPP variations and climatic factors. Further, different land use and vegetation scenarios from 2001 to 2020, as well as the pattern of NPP variations under pure climate scenarios simulated by the Miami model, were used to derive the final maximum potential of NPP and the maximum increment of NPP in Xinjiang. The results showed that: (1) The NPP in Xinjiang showed an upward trend with fluctuations from 2001 to 2020; (2) Among the climatic factors, precipitation had the maximal impact on NPP in Xinjiang; (3) Among the primary land use types in Xinjiang, cultivated land had a large NPP which showed an increasing trend; (4) The increment potential of NPP in Xinjiang was 79.43 g C·m-2. This study can provide a reference for Xinjiang to respond to the national call for “carbon peak” and “carbon neutrality” and to implement ecological restoration and cultivated land protection measures. Figures and Tables | References | Related Articles | Metrics

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Temporal and spatial variations of human activities and landscape ecological risks in the Tarim River Basin, China, during the last 20 years YANG Rongqin, XIAO Yulei, CHI Miaomiao, MU Zhenxia 2024, 41 (6):  1010-1020.  doi: 10.13866/j.azr.2024.06.10 Abstract ( 120 )   HTML ( 0 )   PDF (10088KB) ( 76 )   Human activity is an essential factor in the intensification of regional ecological risk. Hence, it is urgent to discuss the impact of human activity intensity (HAI) on the landscape ecological risk. This paper took the Tarim River Basin as the research object. Based on the land use, population spatial distribution, and night light data during five periods from 2000 to 2020, it introduces the comprehensive index of land use degree to improve the evaluation system of HAI and quantitatively evaluates the temporal and spatial changes of landscape ecological risk (LER) in the basin under robust human activity. Combined with the Copula function and bivariate local spatial autocorrelation model, the spatiotemporal correlation between LER and HAI is revealed. The results showed that (1) The HAI in the Tarim River Basin enhanced markedly in the past 20 years, and extensive human activities were mainly distributed in the oasis areas with rich water resources. The intensity of human activities in the basin increased, with the proportion of low-intensity areas diminished by 17.88% and that of medium-high-intensity areas elevated by 3.57%. (2) The overall LER in the Tarim River Basin was characterized by a high surrounding area and a low central area, and the high-risk area was mainly distributed in the oasis areas with more frequent human activities. The LER in the basin intensified before 2015, which slowed down after 2010, and gradually emerged after 2015. (3) The HAI and LER were positively correlated during the past 20 years, and the positive effect of human activities on LER was enhanced. After 2010, the increasing correlation between the two flattened, and a positive effect appeared in the stage of transition from increase to decrease. The H-H cluster area elevated in space, and the distribution pattern changed from dispersion to concentration. After 2015, the L-L and H-L cluster areas slowly increased, unlike the L-H cluster areas. The results can provide a scientific reference for the rational use of land resources and protection of the landscape ecology in the Tarim River Basin. Figures and Tables | References | Related Articles | Metrics

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Spatio-temporal evolution and driving factors of land use and ecosystem service value in the Lhasa River Basin, China ZHOU Jianwei, LUO Jun, MA Xueyang 2024, 41 (6):  1021-1031.  doi: 10.13866/j.azr.2024.06.11 Abstract ( 137 )   HTML ( 2 )   PDF (11972KB) ( 57 )   Change in land use profoundly impacts ecological development, posing a consequential threat to the sustainable progress of society, civilization, economy, and the environment. Based on high-precision land use data from 2000 to 2020, this study delves into the spatiotemporal evolution of land use and ecosystem service value (ESV) in the Lhasa River Basin. By employing PLUS models and geographic detectors, the driving factors of land use alterations and the spatial differentiation of ESV were explored. The findings reveal that (1) The predominant land use in the Lhasa River Basin was grassland from 2000 to 2020, constituting 85.23% of the total basin area, indicating a trend of grassland reduction and expansion of other land types; specifically, the grasslands decreased by 2.45%, while construction land, water area, and forest land expanded by 199.72%, 44.64%, and 21.97%, respectively. (2) The change in land use within the watershed was intricately influenced by factors such as altitude, annual average ground temperature, and distance from lakes and reservoirs. Altitude, in particular, exhibited a substantial contribution to the expansion of cultivated, forest, water bodies, and construction lands, with respective values of 0.18, 0.11, 0.28, and 0.13. Slope and annual average ground temperature contributed significantly to changes in grass and unused lands, registering values of 0.14 and 0.15, respectively. (3) From 2000 to 2020, the overall ESV of the watershed increased by 1.14% (1.496 billion yuan). Grassland and climate regulation were the land use and ecosystem service types with the most prominent respective contributions of 87.13% and 25.50% to the ESV. (4) Furthermore, the ESV within the watershed exhibited substantial spatial differentiation, influenced by factors including NDVI, altitude, annual average wind speed, and annual average temperature. The explanatory power of NDVI reached a notable 0.46, and the interaction between any two factors accentuated ESV differentiation. These research outcomes provide valuable scientific insights for guiding the spatial planning and ecological and civilizational development of the Lhasa River Basin and analogous regions. Figures and Tables | References | Related Articles | Metrics

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Ecosystem services trade-offs and synergies drived by landuse changes in Ningxia DONG Pengbei, REN Zongping, LI Peng, WANG Kaibo, HE Guokai, WANG Pu 2024, 41 (6):  1032-1044.  doi: 10.13866/j.azr.2024.06.12 Abstract ( 103 )   HTML ( 1 )   PDF (20564KB) ( 43 )   Ningxia is an important region in Northwest China. Thus, it is imperative to study land use change and its impact on ecosystem services to improve the ecological environment of Ningxia and put forward environmental protection measures for the future. However, previous studies have primarily focused on the changes in the ecosystem services during historical periods but lacked a prediction of the ecosystem services and their trade-offs and synergistic relationships under future scenarios. Therefore, this study simulated the land use status under three future scenarios, quantified the four ecosystem services of carbon storage, soil conservation, water yield, and grain yield under the different land use types, and ascertained their trade-offs and synergies at various spatial scales. The main conclusions are as follows: in the future, the water yield of the three scenarios was lower than that of the current year, and the soil conservation and carbon storage were the largest in the ecological protection scenario, reaching 7.98×107 and 4.72×107 tons, respectively. In contrast, the grain yield was the largest in the farmland protection scenario, reaching 1.52×107 tons. The trade-off relationship between ecosystem services mainly occurred between the regulating and supplying services and the synergy relationship between the regulating services. At the provincial scale, only carbon storage and soil conservation services demonstrated a high synergistic relationship; at the regional and county scales, the synergy between water yield and carbon storage services was also remarkable. Figures and Tables | References | Related Articles | Metrics

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The evolution of ecological quality in Yanchi County based on the SA-RSEI model HOU Jiaye, LI Jianhua, WANG Jiarong, MA Haitao, QIANG Zekai, FAN Xingang 2024, 41 (6):  1045-1058.  doi: 10.13866/j.azr.2024.06.13 Abstract ( 111 )   HTML ( 6 )   PDF (12377KB) ( 23 )   This study explored the characteristics and driving factors of the dynamic spatio-temporal changes in the ecology and environment in Yanchi County by using remote sensing images from 1990 to 2020 as the data source and the SA-RSEI as a basis. By combining the Theil-Sen Median analysis, Mann-Kendall significance test, and Hurst index, the pattern of spatiotemporal variations in the ecological and environmental quality of Yanchi County was analyzed. The driving factors of this quality were explored by employing the Geography Detector. The results showed that (1) SA-RSEI initially reduced and then enhanced from 2000 to 2020. (2) The ecological and environmental quality showed an evolutionary process of “initial degradation and then recovery” during these 21 years. The spatial distribution pattern gradually changed from “poor in the south and good in the north” to “good in the southeast and poor in the northwest.” (3) During the 21 years, the ecological and environmental quality of Yanchi County generally degraded, but the degree of degradation gradually reduced, and the degree of ecological and environmental improvement gradually increased after 2020. (4) DI, precipitation, elevation, and GDP are the main factors influencing the spatial variation in regional ecological quality. (5) The interaction between DI, temperature, precipitation, elevation, and other detection factors plays a leading role; the influence of economic factors on SA-RSEI gradually enhances. Figures and Tables | References | Related Articles | Metrics

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Spatiotemporal pattern of NEP in Aksu River Basin based on PLUS land use simulation LI Peiyao, WANG Xinjun, XU Shixian, GAO Shenghan, XUE Zhixuan, HENG Rui 2024, 41 (6):  1059-1068.  doi: 10.13866/j.azr.2024.06.14 Abstract ( 128 )   HTML ( 5 )   PDF (7461KB) ( 100 )   Net Ecosystem Productivity (NEP) is a crucial indicator for assessing the carbon sequestration capacity of terrestrial ecosystems, and Land Use/Cover Change (LUCC) is a key factor influencing regional differences in carbon uptake. Analyzing the trends of LUCC and NEP is essential for achieving regional carbon peaking and carbon neutrality goals. Based on the LUCC and MODIS remote sensing data from 2000 to 2020 in the Aksu River Basin, the annual average carbon sequestration rate of each land use/cover type in the region was estimated. The LUCC for the next 40 years was simulated by the PLUS model, and the spatial and temporal trend of NEP for the next 40 years in the river basin was predicted. The results show that: (1) the total NEP in the basin has shown an increasing trend in the past 20 years, with an uptake rate of 0.136 Mt C·(10a)-1, and the average carbon sequestration rate of forest area is the highest; (2) the total carbon uptake in the Aksu River Basin will continue to increase in the future 40 years. The increase in forest area is the main way of increasing carbon uptake in the Aksu River Basin, and the positive role of ecological protection projects plays a key role in this process. Figures and Tables | References | Related Articles | Metrics

Agricultural Ecology

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Estimation of nitrogen contentration in winter wheat leaves based on hyperspectral images of UAV SUN Fafu, LAI Ning, GENG Qinglong, LI Yongfu, LV Caixia, XIN Huinan, LI Na, CHEN Shuhuang 2024, 41 (6):  1069-1078.  doi: 10.13866/j.azr.2024.06.15 Abstract ( 119 )   HTML ( 5 )   PDF (13024KB) ( 77 )   Established leaf nitrogen concentration (LNC) is the response of crop photosynthesis, an important index of nutrition and growth. To accurately and efficiently estimate different growth period of winter wheat LNC, with the new winter 22 as the research object, using the (UAVs) Pika L hyperspectral cameras for four key growth period of winter wheat canopy reflectance data. The LNC-sensitive spectral index was screened based on the band optimization algorithm and correlation analysis. Stepwise regression, multiple linear regression, and partial least squares regression were combined to establish the estimation model of winter wheat LNC in each key growth stage, which was compared with the single variable estimation model. The results showed that (1) the correlation between the combined spectral index screened using the band optimization algorithm and LNC was stronger than that obtained using the traditional vegetation index and was extremely significant; (2) the combined spectral index in the single variable LNC estimation model allowed to obtain a more accurate model compared with the traditional vegetation index, including Yang flowering DSI(R940, R968) estimate model is set up, best R2 of 0.789. The multi-variable estimation models were more accurate than the single variable estimation models and, among them, the LNC estimation model based on partial least squares regression was the best, and the fitting effect of the booting and flowering stages was better. This model had a coefficient of determination of 0.923 and root-mean-square errors of 0.082 and 0.084. The results of this study provide a theoretical basis and technical support to estimate the LNC of winter wheat and monitor its growth. Figures and Tables | References | Related Articles | Metrics

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Characterization of the freezing injury to Juglans regia at different slope positions in the West Tianshan valley of Xinjiang, China LIU Huaqing, WANG Bo, JIA Yanyan, XIE Xinran, ZHANG Wei 2024, 41 (6):  1079-1088.  doi: 10.13866/j.azr.2024.06.16 Abstract ( 146 )   HTML ( 7 )   PDF (1567KB) ( 96 )   Severe freezing injury has a significant impact on the growth and development of walnuts (Juglans regia), even leading to plant death in some cases. This study employed the sample method to examine the freezing injury to J. regia in the Wild Walnut Nature Reserve located in the West Tianshan valley in Xinjiang. The distribution characteristics of freezing injury among J. regia were analyzed, and the influence of tree height, crown width, and slope position on the extent of freezing injury was investigated. The results indicated that (1) the total freezing injury rate of J. regia was 87.1%. Among these, the proportion of plants with grade 2 freezing injury was the largest (43.4%), followed by grade 1 (22.5%), grade 3 (17.5%), and grade 4 (3.7%). (2) the proportion of freezing injury in J. regia plants was the largest in the middle of slope (46.5%), followed by the bottom (35.9%), and the top (4.7%); the proportion of uninjured plants was the maximum at the top of slope (7.4%), followed by the bottom (3.3%), and the middle (2.2%). (3) the proportion of freezing injured plants in the six height classes (H) was most prominent in H1 (43.4%), followed by H4 (19.5%), H6 (17.0%), H5 (15.7%), H3 (4.3%), and H2 (0.1%). (4) the proportion of freezing injured plants in the six crown width classes (CW) was most extensive in CW1 (43.4%), followed by CW4 (22.1%), CW3 (20.3%), CW5 (9.5%), CW2 (2.9%), and CW6 (1.8%). (5) the proportion of freezing injured plants in different H and CW classes at the same slope position differed significantly (P<0.05). Plants with grade 1 and 2 freezing injuries were mainly restricted to the middle and bottom of the slope, and those with grade 3 and 4 injuries to the middle. (6) freezing injury in plants was markedly correlated with diameter at breast height (P<0.05) and extremely negatively correlated with CW (P<0.01). Most J. regia plants in the Reserve suffered from freezing injury, and the proportions of freezing injury grades varied conspicuously among the different slope positions and different H and CW classes. The results of this study provide a scientific reference for the management of the Wild Walnut Nature Reserve and the prevention of freezing injury in J. regia. Figures and Tables | References | Related Articles | Metrics